Radiation cannot be detected by human senses. A variety of
instruments are available for detecting and measuring radiation.

Examples of radiation survey meters:

This probe is used for the detection of alpha radiation.

The most common type of
radiation detector is a Geiger-Mueller (GM) tube, also called a Geiger counter.

Using a Typical
Geiger-Mueller (GM) Counter to Survey

Get the GM counter and batteries from
storage; prepare the instrument and determine background level.

Preparing the Meter:

Position the Geiger counter with the meter
away from you. Locate and open the battery compartment.

Put the batteries in the meter using proper
orientation (up/down).

Close and latch the battery compartment.

Check the batteries using the
"range" switch or "bat" button; the method depends on the type of
instrument. The meter needle should move to area on scale marked battery, indicating the
batteries are good. If the batteries are not good, find a flashlight or other source of 2
D-cells and put them in the meter -- check these batteries also.

Turn the "F/S" switch to
"S" (Slow).

Turn the "audio" switch to
"ON."

Measuring the Background Radiation:

Check that the "F/S" switch is on
"S" (Slow).

Move the range switch to the most sensitive
position.

Remove the probe cover if one is in place.

Measure the background radiation for 60
seconds: write down the reading. Since background radiation varies with time, it
may be desirable to make several counts and average the results. Record the reading.

Expect a reading of 40-100 counts/min or a
reading of approximately 0.02 mR/hr (i.e. 0.2 on the 0.1 range setting), or 0.2 micro
Sv/hr.

Set the instrument selector switch to the
most sensitive range of the instrument.

Holding the probe approximately 1/2 to 1
inch from the persons skin, systematically survey the entire body from head to toe
on all sides.

-- Move the probe slowly (about 1
inch per second).

-- Do not let the probe touch anything.

-- Try to maintain a constant distance.

-- Pay particular attention to hands, face
and feet.

-- Note that some GM instruments cannot
detect alpha radiation and some low-energy beta radiation. Because alpha radiation is
non-penetrating, it cannot be detected through even a thin film of water, blood, dirt,
clothing, or through probe cover.

An increase in count rate or exposure
rate above background indicates the presence of radiation.

-- Locate the point that produces the most
clicks. (Turn the "F/S" switch to "S" to take a reading at this
location. Remember to reset it to "F" before continuing survey.)

-- When necessary, adjust the range of the
instrument by moving the range selector switch.

-- Document time and radiation
measurements.

-- In general, areas that register more
than twice the previously determined background level are considered contaminated. For
accidents involving alpha emitters, if the reading is less than twice the background
radiation level, the person is not contaminated to a medically significant degree. If the
accident circumstances indicate that an alpha emitter (such as plutonium) or low energy
beta emitter could be a contaminant, a health physicist should always be consulted.